First we had the blue/black/gold dress, then there was the wall with the cigar… now the latest puzzle to sweep the web is a question of horses, horseshoes and boots.

The puzzle involves a simple set of sums with each symbol representing a number. All you have to do is work out which number each symbol represents. The first three sums have correct answers to give you a start.

The quiz has been viewed, if not solved, by more than half a million people in the past couple of days. Take a look for yourself and see if you can crack it, but be warned, it has been described as “tricky”.

There have been several answers put forward online but the general consensus is that the correct answer is 21.

The final sum is worked out by first using the other three completed sums to give each symbol its value.

Three horses added together equalling thirty means that each horse itself is worth ten.

Once you know that, you can work out that a horseshoe is worth four because two of them added to one horse is worth eighteen.

Lastly, two boots are worth two, on the basis that when taken away from the horseshoe (four) you are left with two. So one boot is worth one.

All fairly simple so far, but the final sum is proving the sticking point for many, not because they have the wrong values but because they are simply not completing the sum in front of them.